In general, an arm robot that works together with human is required to have high safety, and, in order to safely operate the arm robot, it is desirable to sufficiently reduce its driving force and assure the safety. However, to achieve both a wider range of motion and a heavier work weight capacity using a typical vertical articulated arm with an arm axis structure similar to a human arm, a large driving force is required especially at a joint of the arm base where a moment length is long. This results in the arm structure which is not very safe and not low power consumption.
On the other hand, assembly work or the like is performed using an industrial robot such as a SCARA (Selective Compliance Assembly Robot Arm) robot combining a horizontal articulated axis and a vertical axis. Further, an articulated robot in which a plurality of stages of offset rotational joints are mounted between a robot main body and an end effector, each offset rotational joint including a rotation control structure mounted on the plane tilted with respect to a link axis line between a driving link and a driven link, the driven link having an offset rotational axis line tilted with respect to the link axis line, is known (see Patent Literature 1, for example).